Jump to content

? for those that have split their cases.


Recommended Posts

Getting ready to put a new crank and bearings in cause I noticed while replacing the timing chain that the crank slides in the bearing on the flywheel side, the one thats supposed to be pressed on. From checking other posts I've noticed many people have said that there crank just pulled out of both main bearings by hand, no tool needed to press it out. So I'm just curiouse, when you seperated your case's was the main bearing on the left side(flywheel side) still tight on the crank or was it able to slide on and off?

Just kind of wondering if its a common occurence or not?

I wouldn't have noticed in mine if I hadn't looked real close, no up or down play, side to side play may be a bit much, never any metal at all on my oil filter and I inspect it real closely, and bike seems to sound fine. The fact that the shaft is probably very slowy weaing were it sits inside the bearing doesn't worry me so much cause the bearing on the right side isn't pressed on and that doesn't cause the shaft to wear but the fact that something made that bearing break loose tells me that that bearing probably has some damage to it even though it seems to feel fine when I spin it.

Link to comment
Share on other sites

I just did a wr400 and I did need to press it off.

I did learn a tip for pressing it back on. Put the crank in the freezer or on dry ice. Find a socket the same size as the inner race on the bearing. Heat the socket with a torch to near red hot and put it on the bearing race for a minute. The crank will slide right in. ONLY do this if your bearing is open on both sides, ie: no seal.

Link to comment
Share on other sites

I've done 4 of them and all four slid right out. We also did a yz450 and it was the same. They are not pressed on the shaft. They are however tight in the case. After you get the crank out and the keepers removed then you may need to heat the case a bit to get it out easily. Apparently the WR400 that motodiver13 did was way different because on the 250 you cannot install the bearing on the crank because you would not be able to get the keepers reinstalled. They are a slip fit on the crank.

Link to comment
Share on other sites

I know that the bearings are put into the case first but I thought that a special tool was needed to pull the crankshaft through the bearing on the left side. Or the case with the bearing already in are heated in the oven and the crankshaft frozen in the freezer and then there assembled together. Thats why I thought the bearing should be tight on the crank on that side. But you guys are telling me it should slide right it in. It would be nice if I didn't have to replace it after all.

Thanks for the reponses

Link to comment
Share on other sites

dave, I did put the bearing into the case first. But the crank to bearing fit is an interferance fit and it did not slide in for me. I tried putting the crank on dry ice alone first but no luck, so I took it to the shop for the installation tool and the mechanic showed me the "hot socket trick"

Link to comment
Share on other sites

I know that the bearings are put into the case first but I thought that a special tool was needed to pull the crankshaft through the bearing on the left side. Or the case with the bearing already in are heated in the oven and the crankshaft frozen in the freezer and then there assembled together. Thats why I thought the bearing should be tight on the crank on that side. But you guys are telling me it should slide right it in. It would be nice if I didn't have to replace it after all.

Thanks for the reponses

I just rebuilt my top and bottom end on my 07 yz250f and yes the old crank and new crank slid out kind of easily. Not like butter but it didn't take much force.

I asked my mechanic about it and he told me that it completely normal for a 4 stroke. I did buy the case splitter and crank puller and ended up not even needing them lol. He did say though, for a 2 stroke engine you do need the splitters and pullers because those engines are much more tight. The splitter did make it a little easier to break the Yamabond holding the cases together. gives you a free hand to hit the sides that arn't coming apart evenly

Good luck!!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

×
×
  • Create New...